MFC当CTreeCtrl控件失去焦点后，保持选中状态的方法（总结）

文章部分内容来源：https://blog.csdn.net/tom_xuzg/article/details/38348741

                                https://blog.csdn.net/daoming1112/article/details/77891525

一. 设置控件属性或样式

       1. 控件属性

 控件Always Show Selection属性设置为True。

       2. 修改样式

如果控件是动态生成的，那么在Create时给dwStyle增加一个属性TVS_SHOWSELALWAYS；

或者调用ModifyStyle函数修改：ctreectrl.ModifyStyle(0, TVS_SHOWSELALWAYS);

以上两种方法当控件失去焦点后被选项的背景颜色会成灰色，不同的系统主题显示不一样，有时候与未选中项很像，仔细看不太明显，因此可以用下面的方法自己设置各种颜色

二. 重载OnNMCustomdraw或OnCustomdraw函数

直接上代码比较直观

void CViewTree::OnNMCustomdraw(NMHDR *pNMHDR, LRESULT *pResult)
{
	LPNMCUSTOMDRAW pNMCD = reinterpret_cast<LPNMCUSTOMDRAW>(pNMHDR);
	// TODO: 在此添加控件通知处理程序代码
	if (this->m_hWnd != pNMHDR->hwndFrom)
		return;

	LPNMTVCUSTOMDRAW pCustomDraw = (LPNMTVCUSTOMDRAW)pNMHDR;
	switch (pCustomDraw->nmcd.dwDrawStage)
	{
	case CDDS_PREPAINT:
		// Need to process this case and set pResult to CDRF_NOTIFYITEMDRAW, 
		// otherwise parent will never receive CDDS_ITEMPREPAINT notification. (GGH) 
		*pResult = CDRF_NOTIFYITEMDRAW;
		return;

	case CDDS_ITEMPREPAINT:  //失去焦点后被选项各种颜色
		if (this->IsWindowEnabled() == 1)
		{
			if ((pCustomDraw->nmcd.uItemState & (CDIS_FOCUS)) == 0
				&& (pCustomDraw->nmcd.uItemState & (CDIS_SELECTED)) == CDIS_SELECTED) // selected
			{
				pCustomDraw->clrTextBk = RGB(0, 128, 220);  //失去焦点后被选项背景颜色
				pCustomDraw->clrText = RGB(255, 255, 255);  //失去焦点后被选项文本颜色
			}
			*pResult = CDRF_NOTIFYPOSTPAINT;
			return;
		}
		else {
			*pResult = CDRF_DODEFAULT;
			return;
		}
	case CDDS_ITEMPOSTPAINT:  //失去焦点后给被选项画一个外框，这个case根据需要可有可无
		if (this->IsWindowEnabled() == 1)
		{
			if ((pCustomDraw->nmcd.uItemState & (CDIS_FOCUS)) == 0
				&& (pCustomDraw->nmcd.uItemState & (CDIS_SELECTED)) == CDIS_SELECTED) // selected
			{
				CRect   rcText;
				HTREEITEM hItem = (HTREEITEM)pCustomDraw->nmcd.dwItemSpec;
				this->GetItemRect(hItem, &rcText, true);
				CPen penBlue(PS_SOLID, 1, RGB(255, 0, 0));  //失去焦点后被选项的外框颜色
				CDC* pDC = CDC::FromHandle(pCustomDraw->nmcd.hdc);
				CBrush* pBrush = CBrush::FromHandle((HBRUSH)GetStockObject(NULL_BRUSH));
				CBrush* pOldBrush = pDC->SelectObject(pBrush);
				CPen* pOldPen = pDC->SelectObject(&penBlue);
				pDC->Rectangle(&rcText);
				pDC->SelectObject(pOldBrush);
				pDC->SelectObject(pOldPen);
			}
			*pResult = CDRF_SKIPDEFAULT;
			return;
		}
		else {
			*pResult = CDRF_DODEFAULT;
			return;
		}
	}
}

推荐第二种方法